In a mobile network, various component carriers may be used by a plurality of mobile devices. During carrier aggregation, a single user equipment (UE) may receive and/or send over a plurality of component carriers. The scheduling of information on the plurality of component carriers may be, in some cases, performed using a scheduling carrier referred to as a primary carrier. Component carriers other than the scheduling carrier are referred to as scheduled carriers, which in some cases are referred to as secondary carriers. Thus, a UE will receive an indication on the scheduling carrier that it should detect a subframe on a scheduled carrier, for example.
When a primary (scheduling) carrier and a secondary (scheduled) carrier have similar subframes allocated to downlink or uplink transmissions, the scheduling of the secondary carrier from the primary carrier is relatively straightforward. Specifically, since both the primary and secondary carriers have identical downlink subframes, a downlink subframe at the primary carrier can be used to allocate resources on a simultaneous downlink resource on the secondary carrier.
However, if the component carriers are configured differently, that is the component carriers have different subframes allocated to downlink than other component carriers, the degree of complexity with regard to scheduling the secondary carrier increases. For example, a secondary carrier may have more downlink subframes which need to be scheduled than the number of downlink subframes at the primary carrier.